Massive collision created moon 4.5 billion years ago

The moon is seen in the night sky over Tel Aviv, Israel, Sunday, June 23, 2013. A new study adds further proof to the hypothesis that the moon was created in a massive collision with another object 4.5 billion years ago.(Photo: Ariel Schalit AP)

CAPE CANAVERAL, Florida (AP) — A new study strengthens the notion that our moon was created by a collision between Earth and a planet-sized object some 4.5 billion years ago.

German scientists studied moon rocks gathered by astronauts nearly a half-century ago in the Apollo 11, 12 and 16 missions. They analyzed various kinds of oxygen atoms and found the moon rocks have a different makeup than Earth rocks do. That fits with the idea that the moon would contain material from the object that struck Earth.

The idea that the moon was created in this way has been called the "Giant Impact Hypothesis."

"I think that most people believe in the Giant Impact Hypothesis," said the study's lead author, Daniel Herwartz, a geologist at Georg-August-Universität in Göttingen, Germany, "and now that we solved one of the last gaps in explaining it, those who criticize it will have a hard time."

The object that hit the Earth has been given the name "Theia."

The results also suggest that the moon may be a 50-50 mix of material from this object and from Earth.